Don't start speech synthesis until after the audio mixer is initialized.

chrome/browser/extensions/extension_tts_api_chromeos.cc

Index: chrome/browser/extensions/extension_tts_api_chromeos.cc
===================================================================
--- chrome/browser/extensions/extension_tts_api_chromeos.cc	(revision 109026)
+++ chrome/browser/extensions/extension_tts_api_chromeos.cc	(working copy)
@@ -2,10 +2,15 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "chrome/browser/extensions/extension_tts_api_chromeos.h"
+
+#include <list>
+
 #include "base/bind.h"
 #include "base/memory/singleton.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop.h"
+#include "base/stl_util.h"
 #include "base/string_number_conversions.h"
 #include "chrome/browser/chromeos/dbus/dbus_thread_manager.h"
 #include "chrome/browser/chromeos/dbus/speech_synthesizer_client.h"
@@ -18,7 +23,17 @@
 const int kSpeechCheckDelayIntervalMs = 100;
 };
 
-class ExtensionTtsPlatformImplChromeOs : public ExtensionTtsPlatformImpl {
+// Very simple queue of utterances that can't be spoken because audio
+// isn't initialized yet.
+struct QueuedUtterance {
+  int utterance_id;
+  std::string utterance;
+  std::string lang;
+  UtteranceContinuousParameters params;
+};
+
+class ExtensionTtsPlatformImplChromeOs
+    : public ExtensionTtsPlatformImpl {
  public:
   virtual bool PlatformImplAvailable() {
     return true;
@@ -37,9 +52,11 @@
   // Get the single instance of this class.
   static ExtensionTtsPlatformImplChromeOs* GetInstance();
 
+  // TTS won't begin until this is called.
+  void Enable();
+
  private:
-  ExtensionTtsPlatformImplChromeOs()
-      : ALLOW_THIS_IN_INITIALIZER_LIST(weak_ptr_factory_(this)) {}
+  ExtensionTtsPlatformImplChromeOs();
   virtual ~ExtensionTtsPlatformImplChromeOs() {}
 
   void PollUntilSpeechFinishes(int utterance_id);
@@ -51,6 +68,8 @@
 
   int utterance_id_;
   int utterance_length_;
+  std::list<QueuedUtterance*> queued_utterances_;
+  bool enabled_;
   base::WeakPtrFactory<ExtensionTtsPlatformImplChromeOs> weak_ptr_factory_;
 
   friend struct DefaultSingletonTraits<ExtensionTtsPlatformImplChromeOs>;
@@ -63,11 +82,26 @@
   return ExtensionTtsPlatformImplChromeOs::GetInstance();
 }
 
+ExtensionTtsPlatformImplChromeOs::ExtensionTtsPlatformImplChromeOs()
+    : enabled_(false),
+      ALLOW_THIS_IN_INITIALIZER_LIST(weak_ptr_factory_(this)) {
+}
+
 bool ExtensionTtsPlatformImplChromeOs::Speak(
     int utterance_id,
     const std::string& utterance,
     const std::string& lang,
     const UtteranceContinuousParameters& params) {
+  if (!enabled_) {
+    QueuedUtterance *queued = new QueuedUtterance();
+    queued->utterance_id = utterance_id;
+    queued->utterance = utterance;
+    queued->lang = lang;
+    queued->params = params;
+    queued_utterances_.push_back(queued);
+    return true;
+  }
+
   utterance_id_ = utterance_id;
   utterance_length_ = utterance.size();
 
@@ -111,14 +145,22 @@
     speech_synthesizer_client->SetSpeakProperties(options);
 
   speech_synthesizer_client->Speak(utterance);
-  ExtensionTtsController* controller = ExtensionTtsController::GetInstance();
-  controller->OnTtsEvent(utterance_id_, TTS_EVENT_START, 0, std::string());
-  PollUntilSpeechFinishes(utterance_id_);
+  if (utterance_id_ >= 0) {
+    ExtensionTtsController* controller = ExtensionTtsController::GetInstance();
+    controller->OnTtsEvent(utterance_id_, TTS_EVENT_START, 0, std::string());
+    PollUntilSpeechFinishes(utterance_id_);
+  }
 
   return true;
 }
 
 bool ExtensionTtsPlatformImplChromeOs::StopSpeaking() {
+  // If we haven't been enabled yet, clear the internal queue.
+  if (!enabled_) {
+    STLDeleteElements(&queued_utterances_);
+    return true;
+  }
+
   chromeos::DBusThreadManager::Get()->GetSpeechSynthesizerClient()->
       StopSpeaking();
   return true;
@@ -130,6 +172,19 @@
           event_type == TTS_EVENT_ERROR);
 }
 
+void ExtensionTtsPlatformImplChromeOs::Enable() {
+  enabled_ = true;
+  while (!queued_utterances_.empty()) {
+    QueuedUtterance* queued = queued_utterances_.front();
+    Speak(queued->utterance_id,
+          queued->utterance,
+          queued->lang,
+          queued->params);
+    delete queued;
+    queued_utterances_.pop_front();
+  }
+}
+
 void ExtensionTtsPlatformImplChromeOs::PollUntilSpeechFinishes(
     int utterance_id) {
   if (utterance_id != utterance_id_) {
@@ -180,3 +235,8 @@
 ExtensionTtsPlatformImplChromeOs::GetInstance() {
   return Singleton<ExtensionTtsPlatformImplChromeOs>::get();
 }
+
+// global
+void EnableChromeOsTts() {
+  ExtensionTtsPlatformImplChromeOs::GetInstance()->Enable();
+}